are you sure it's the HD version and not the Classic game?

It does that sometimes. Just play it for a few minutes, and it'll show up properly on Steam. And then you'll be able to enter giveaways for this.

Sucks, but it's 100% Steam's fault. It can be a bit wonky at times when it comes to your games library. ^^;

Same with me, but SS HD Second Encounter doesn't even show up on my games list. I believe it's because there used to be a free multiplayer mode of the game (You know how F2P games don't show up on your games list unless you run them).

You can make the game show up on your list by running it for 6-10 mins. If you can't download the game, you can use SAM (Steam Achievement Manager) to trick the game into thinking you're running the game. I think it's fine (it has been for me) as long as you don't unlock any achievements.

Did you buy the version from the Humble Bundle? If so for some reason SS2: HD doesn't show up on your games list. I haven't tried playing for a few minutes yet, but that is one possible fix. Another is to contact support at steam and ask for the game to be added to your games list on your profile.

Same problem here too. Running it for 10 minutes solved for me. Thanks for the tip, Alecry.

Missing Base Game either :(